(1) Field of the Invention
This invention relates to an apparatus for the automatic sheet treatment of wafers by plasma reaction, and more particularly to an apparatus for the treatment of the wafer by plasma reaction with an improved wafer carrying means.
(2) Description of the Prior Art
Recently, etching of a semiconductor wafer, as well as removal by ashing of a photoresist by use of an apparatus for the treatment of wafer materials by gas plasma reaction, has become widely available in semiconductor wafer production processes. The apparatus for the treatment of wafer by plasma reaction can be classified into two major types, that is, a batch type in which 10 to 25 sheets of wafers are set in a horizontal reaction tube for the simultaneous treatment thereof, and an in-line type in which wafers are subjected to the automatic one-by-one treatment thereof. Recently, the latter type has become widely available with the advantages such as a narrow scatter of results from the treatment of respective wafers, high processing precision, and a short treating time for each sheet of wafer. Further, various kinds of automatic wafer carrying means have been proposed.
U.S. Pat. No. 4,208,159 discloses a wafer carrying system using an arm provided with a pick up, and further discloses a wafer carrying system using a belt conveyor.
Japanese utility Model Application No. 124709/1979 discloses a wafer carrying system of a wire conveyer type, which is widely used for practical apparatuses because of its excellent advantages.
These wafer carrying systems described above are all of such a type that the vacuum of the reaction chamber is broken every time a wafer is taken in or out of the reaction chamber, and are unsuitable for such an apparatus as used in etching of an aluminium wiring, where a preliminary vacuum chamber is required to be provided for obtaining a high vacuum in the reaction chamber. However, it is very difficult to place the only wafer carrying means in the preliminary vacuum chamber due to the structure of the apparatus for the treatment of wafers by plasma reaction. Thus, the apparatus for the treatment of wafers by plasma reaction must be wholly placed in the preliminary vacuum chamber. This is very complicated and economically undesirable. Therefore, the wafer carrying means placed in the preliminary chamber is required to be compact and simplified in structure in order to obtain a high vacuum in the reaction chamber.
U.S. Pat. No. 4,149,923 also discloses an automatic apparatus for the treatment of wafer materials by plasma reaction, in which a preliminary vacuum chamber is provided before and behind the reaction chamber and all elements of the apparatus are installed on an inclined base table to effect the downward movement of the wafer as a wafer carrying means, where the wafer is stopped as required by a wafer stopper. Accordingly, there is the disadvantage that the wafer is liable to be damaged by the stopper upon stopping the wafer.